A rill in a barnyard and the Grand Canyon represent, in the main, stages of valley erosion that began some millions of years apart.

The meaning that we are seeking in evolution is its meaning to us, to man. The ethics of evolution must be human ethics. It is one of the many unique qualities of man, the new sort of animal, that he is the only ethical animal. The ethical need and its fulfillment are also products of evolution, but they have been produced in man alone.

The opposition to teaching evolution is, of course, almost always given a religious reason. That may usually be its real basis, but I think it is often a mask, perhaps unconscious, for underlying anti-intellectualism or antiscientism.

The search for historical laws is, I maintain, mistaken in principle.

Recognition of this kinship with the rest of the universe is necessary for understanding him, but his essential nature is defined by qualities found nowhere else, not by those he has in common with apes, fishes, trees, fire, or anything other than himself.

Splitting and gradual divergence of genera is exemplified very well and in a large variety of organisms.

It is inherent in any definition of science that statements that cannot be checked by observation are not really saying anything or at least they are not science.